Field of the Invention:
The present invention relates to novel organopolysiloxane compositions that are storage-stable in the absence of moisture, but curable into self-adhesive elastomeric state in the presence thereof, and, more especially, to novel storage-stable organopolysiloxane compositions containing an .alpha.,.omega.-dihydroxydiorganopolysiloxane, a ketiminooxysilane crosslinking agent and a bonding agent which comprises (i) admixture of an aminoorganosilicon compound bearing a primary amine substituent and an organosilicon compound bearing an epoxy functional group, or (ii) reaction product between such aminoorganosilicon/epoxyorganosilicon compounds.
Description of the Prior Art:
One-component organopolysiloxane compositions containing a ketiminoxysilane crosslinking agent, and, generally, also an inorganic filler and a curing catalyst have long been known to this art. Such compositions are described, for example, in FR-A-1,314,649, FR-A-1,371,250, U.S. Pat. Nos. 3,678,003 and 3,986,999, in GB-A-1,468,467, in BE-A-901,479 and in EP-A-157,580.
These compositions are particularly useful in coating and jointing applications and, notably, as sealing agents in the construction industry for producing glazed structures.
For this particular application, the hardened elastomer must have a relatively low modulus of elasticity and, above all, adhere strongly to glass and to the material forming the structure in which the glass is mounted, such as wood, aluminum, concrete, PVC (polyvinyl chloride), natural and synthetic rubbers, stone, earthenware and brick.
However, the elastomers produced from compositions containing ketiminoxysilane crosslinking agents generally exhibit insufficient bonding to certain substrate materials employed in the construction industry, aluminum and PVC in particular. Various additives have been proposed to this art for incorporation into such compositions with a view to remedying this deficiency.
Thus, BE-A-901,479 proposes the use of titanium complexes, certain of which are described as crosslinking catalysts in FR-A-2,531,095.
FR-A-2,074,144 describes the use of an amino functional silane as a bonding agent in a composition containing a ketiminoxy compound. These bonding agents have also been used (for the same application) in compositions comprising a polyalkoxysilane crosslinking agent (see particularly EP-A-021,859). Such bonding agents are presented as not influencing the storage stability of the hardenable elastomer-forming starting materials without being any the less efficient.
The following are typical examples of this class of bonding agents:
(C.sub.2 H.sub.5 O).sub.3 Si(CH.sub.2).sub.3 NH.sub.2 (.gamma.-aminopropyltriethoxysilane); PA0 CH.sub.3 (C.sub.2 H.sub.5 O).sub.2 Si(CH.sub.2).sub.3 NH.sub.2 (.gamma.-aminopropylmethyldiethoxysilane); PA0 (CH.sub.3)(CH.sub.3 O).sub.2 Si(CH.sub.2).sub.3 NH(CH.sub.2).sub.2 NH.sub.2 (.gamma.-(.beta.-aminoethylamino)propylmethyldimethoxysilane).
U.S. Pat. No. 4,115,356 describes a trialkoxysilane bearing an epoxy functional group useful as a bonding agent for silicone elastomer compositions comprising a polyacyloxysilane crosslinking agent.
A typical such silane is: ##STR1## .gamma.-glycidoxypropyltrimethoxysilane.
It is also known to the art that a bonding agent comprising the reaction product or a simple mixture of an aminopolyalkoxysilane and an epoxypolyalkoxysilane may be used in two-component (EP-A-178,751) and one-component (EP-A-221,644) silicone elastomer compositions containing polyalkoxysilane crosslinking agents. The preferred silanes are those indicated above.
In Japanese Pat. Application KOKAI 79/90,348, the product of a reaction between an organic primary amine and an epoxy functional polyalkoxysilane is described as a bonding agent in one-component compositions containing ketiminoxysilane crosslinking agents. The amino functional polyalkoxy-silanes are explicitly excluded because they lead to yellowing of the composition.
In consideration of the above prior art, it would appear that the amino functional polyalkoxysilanes have already been described as bonding agents for both classes of silicone elastomer compositions, those comprising alkoxy crosslinking agents and those comprising ketiminoxy crosslinking agents.
Nonetheless, one cannot extrapolate from one class of silicone compositions to another in respect of mutual efficacy of such bonding agents. This has been demonstrated in French Patent Application 86/12,892, filed Sept. 11, 1986, and assigned to the assignee hereof.
Furthermore, as shown in the comparative examples in this '892 application, it appears that the bonding agents of the prior art, in compositions comprising ketiminoxysilane crosslinking agents, exhibit at least one of the following drawbacks:
(1) The storage stability of the compositions is adversely affected by the presence of the bonding agent; PA1 (2) Crosslinking of the compositions into elastomers is too slow, particularly at room temperature; PA1 (3) The bonding agent does not provide for adequate adhesion of the elastomer to a given substrate; PA1 (4) The physical properties of the elastomer are mediocre or distinctly deficient, particularly for jointing applications; and PA1 (5) The elastomers are objectionably discolored by the bonding agent. PA1 (i) an aminoorganosilicon compound C.sub.1 bearing at least one amino functional group and comprising a primary amine substituent; and PA1 (ii) an organosilicon compound C.sub.2 bearing at least one epoxy functional group and having from 4 to 20 carbon atoms, in a ratio of 0.5 to 4 equivalents of primary amine group of C.sub.1 per one equivalent of epoxy functional group in C.sub.2 ; PA1 (a) oils of the formula HO[Si(CH.sub.3).sub.2 O].sub.y H, in which the symbol y represents any number ranging from 2 to 22; PA1 (b) resins in which the CH.sub.3 / Si ratio is 1.6 or higher, containing at least 2% by weight of hydroxyl groups, principally comprised of recurring units of the formulae (CH.sub.3).sub.3 SiO.sub.0.5, (CH.sub.3).sub.2 SiO and CH.sub.3 SiO.sub.0.5 ; PA1 (c) methylpolysiloxane resins MQ comprising (CH.sub.3).sub.3 SiO.sub.0.5 recurring units (M) and SiO.sub.2 recurring units (Q), with an M/Q molar ratio ranging from 0.4 to 1.2 and having an OH weight content of 2 to 6%.